Tube expanding mill



May 2, 1933. R. c. STIEFEL TUBE EXPANDING MILL Filed April 16, 1930 2 Sheets-Sheet 1 fl; INVENTOR WITNESS E5 2, 1933. R. c. STIEFEL TUBE EXPANDING MILL Filed April 16, 1930 2 Sheets-Sheet 2 WITNESSES mad z I Patented May 2, 1933 PATENT OFFICE RALPH C. STIEFEL, OF ELLWOOD CITY, PENNSYLVANIA TUBE MILL Application filed April 16,

The invention relates to cross or skew-roll mills for expanding the diameters of seamless tubing. Y

Mills of the type herein contemplated comprise a pair of rolls, herein designated as skew rolls, for engaging the outer, and a mandrel arranged between the rolls for engaging the inner wall surface of a tube, the

tube-engaging or working faces of the rolls and mandrel forming a pass in which the wall thickness of a tube is decreased, and its diameter increased or expanded. As heretofore formed by the skew rolls and mandrel, the working passes of these mills have been such that a longitudinatmovement of the mandrel with relation to the rolls varies the minimum thickness of the pass, or in other words the draft upon the walls of tubing.

Usually, the working faces of the rolls and.

mandrels both taper outwardly the former less than the latter, to form a gradually diminishing pass. Consequently, when a mandrel has been so initially positioned or adjusted with relation to the skew rolls as to form a pass for reducing the wall thickness of tubing a definite amount, the thickness of pass is diminished by the thermal expansion of the mandrel and its supporting mandrel .bar due to the heat of the tubing being expanded, and the draft upon the tubing is correspondingly increased. This has resulted in undesirable variations in the wall thicknesses of expanding tubing, as well as in undesirable variations in their expanded diameters due to variations in their wall thicknesses.

The object of this invention is to provide a tube expanding mill of the type described,

' 40 the expanding passes of which are so formed that normal variations, such as those consequent upon thermal expansion or contrac-- tion of a mandrel bar, in the longitudinal position of the mandrel. with relation to the rolls, do not result in a variation in the draft of the pass.

A further object is to provide a tube ex panding mill of the type described having. a plurality of passes so formed with relation to each other that the torsional effect tending to 1930. Serial No. 444,706.

twist or distort the minimum.

The invention is illustrated in the accompanying drawings, of which Fig. 1 is a some what diagrammatic view of an expanding mill embodying the invention; Fig. 2 a sectional view taken on the line II II,- Fig. 1; Fig. 3 a view similar to Fig. 1 showing a modification of construction; and Fig. 4 an enlarged view of a portion of the expanding passes of the mill of Fig. 1, illustrating its tube-expanding action,

The mill provided according to this invention. comprises a pair of skew rolls, which may be of either barrel or mushroom type, but is preferably of the latter. Between the rolls there is a mandrel supported by a mandrel bar and forming with the rolls a tubeexpanding pass of constant draft regardless of normal variations in the longitudinal movement of the mandrel with relation to the rolls. The skew rolls are provided with conical working faces so shaped and disposed that at the time of their engagement with the outer wall of a tube they are parallel to the axis of the tube or slightly taper inwardly in the direction of movement of the tube through the mill, and the mandrel is provided with a conical working face which tapers outwardly in the direction of movement of a tube through the mill or is parallel with the axis of the tube. By so forming the tube-engaging pass, the draft made upon the wall of a tube remains constant regardless of the normal variations in the longitudinal position of the mandrel after it has been initial- 1y positioned in a given setting with relation to the skew rolls.

Having reference now to the illustrative Y embodiments of the invention, and first to that shown in Fig. 1, a pair of mushroom type skew rolls "1 and 2 are so mounted with relation to each other, and to a mandrel 3 arranged between them, that when the rolls are rotated in the customary manner they cause a tube or tubular blank 4 to advance spirally in the pass formed between the mandrel and the working facesof the rolls. Because the mounting of such rolls, as well as the means for driving them, are so well known, they m tubing is reduced to a are not here illustrated. These rolls, which are alike, and mandrel 3 which cooperates with them, are provided with working faces forming two expanding passes for tube 4. Each roll is illustrated as being provided with conical working faces 5, 6, 7 and 8, each of which is a segment of a cone, although the several cones of which each is a segment have their elements inclined at different angles to the axis 9 of the roll. Mandrel 3 is provided I with two working faces 10 and 11, shaned in the manner presently to be explained, and which cooperate with the working faces of the rolls to form two tube-expanding passes.-

only a portion'of the mandrel and of one ofthe rolls. The working face 5 of each roll is so shaped that at the time it engages the outer wall of a tube it tapers inwardly in the direction of the movement of the tube through the mill. Accordingly, this working face presses the tube inwardly upon the work-- ing face 10 of mandrel 3, which. as shown, tapers outwardly in the direction of movement of the tube. The wall of the tube being thus spirally rolled between these work mg faces of therolls and the mandrel, becomes reduced in thickness, and the circumference of the'tube is correspondingly enlarged so that the tube assumes the general elliptical form shown in Fig. 2. The work mg face 6 of the roll, and the working face of the mandrel adjacent to it, are each preferably parallel to the axis of the tube.

At the end of the portion of the pass formed exteriorlv by the working faces 6, each roll has an offset 15 extending beyond engagement of the outer surface of the wall of the tube as it emerges from the first pass of the mill. At this ofl'set portion of the rolls, the tube, being unconfined, becomes progressively changed from its substantially elliptical to a substantially round form. Thus the tube s of proper form to enter the second expandmg pass, which is formed between the work ing faces 7 of the rolls-and the working face 11- of the mandrel. The working faces 7 of the rolls are such that at the time they engage the outer surface of the wall of a tube they are parallel to the axis of the tube, while the working face 11 of the mandrel first tapers outwardly in the direction of longitudinal movement of the tube. and then becomes cylindrical. There is thus formed a pass which gradually diminishes in thickness and increases in draft for further reducing the thickness of the tube and correspondmgly increasing its circumference. In this expanding pass, as in the first pass, the tube is given the general elliptical shape indicated in Fig. 2, while beyond this pass the tube gradually assumes a circular form against the face 8 of the rolls, the tube being then unconfined interiorly.

If it he assumed that the relative position of the rolls and mandrel are originally that illustrated in Fig. 4, it will be seen that their working faces are such that thermal expansion or contraction of mandrel bar 12 does not vary the thickness or draft in either of the expanding passes. Expansion of the mandrel merely shortens the gap between the offset 15 on the rolls and the correspondingly opposed offset between working faces 10 and 11 of the mandrel, and contraction lengthens it. Accordingly, tubes or tube blanks 4 of uniform diameters and wall thicknesses may be successively expanded to desired uniform diameters and wall thicknesses.

To further illustrate the action of the mill for a given setting, dot-and-dash line 16 shows the major axis of a tube at each point transversely of the tube in a plane per endicular to that of Fig. 4, while dot-andash line 17 indicates the corresponding diameter of the tube if it were circular in cross section at all points throughout its passage, through the mill. Proceeding from left to right along line 16, the tube is gradually, and with increasing rapidity, changed from its round to its elliptical form in the first pass of the mill; it then becomes substantially circular as it enters the second pass; it is then again changed to elliptical form in the second pass; and finally gradually assumes itscircular form beyond the second pass adjacent to the working faces 8 of the rolls.

In Fig. 3 there is shown a mill comprising a pair of rolls 20 and 21 and a mandrel 22 provided with an increased number of working faces similar to those of the mill of Fig. 1 for forming three expanding passes. These expanding passes may be formed the same as those of Figs. 1 and 4, as will be clearly seen by a comparison of the drawings.

In the practice of the invention, a tube may be expanded without elongating it, or it may be simultaneously expanded and elongated.

This is determined by the angle of flow between the adjacent working faces of the rolls and mandrel in the passes. If this angle, which is that of the inclination of one to another of cooperating working faces, is relatively large so that there is a consequent large reduction in the thickness of a tube within a relatively short length in the axial direction of the blank, the tube may be elongated as well as expanded, while by the use of smaller angles of flow the tube may be merely expanded. If any elongation of a 10 uniform peripheral speed planes lie substantially in the longitudinal centers of the passes. In Fig. 4 these planes are indicated at points 25 and 26, both of which lie on a dot-anddash line 27 which passes through the intersection of the axes of the rolls and that of the mandrel. By maintaining this relation between the line 27 and the axes of the mandrel and the rolls, the relation between the diameters of the tube is the same at both points 25 and 26. Therefore, the rolls tend to revolve the tube with the same angular speed at both of these points, thus eliminating torsional effect on the tube substantially at the center of each pass. On each side of points 25 and 26 a uniform relation between diameter of roll and corresponding diameter of tube is not maintained on account of the elliptical shape of the tube. Therefore a slight difference of surface speedor slip between rolls and tube exists on each side of points 25 and 26. However, by maintaining even angular tube speeds at the centers of the several passes the torsional effect on the tube, or the slip between tube and roll surfaces, is thereby eliminated, and torsional effect or slip is reduced to a minimum at each side of the centers of the passes.

The longitudinal extent of each pass is made greater than that of the longitudinal advance of the tube during a half of its revolution, because otherwise the tube would become spiralled with adjoining thick and thin portions.

According to the provisions of the patent statutes, I have explained the principle and operation of my invention, and have illustrated and described what I consider to represent the best embodiments of it. However, I desire to have it understood that, within the scope of the appended claims, the inven tion may be practiced otherwise than as illustrated and described.

I claim as my invention:

1. A tube expanding mill, comprising a pair of skew rolls for engaging the outer surface and an interposed mandrel for engaging the inner surface of the wall of a tube, said rolls and mandrel being provided with working faces forming a plurality of successive tube-expanding passes of successively increasing diameters and each of constant draft regardless of normal variations in the longitudinal position of the mandrel with relation to the rolls, said rolls between diameters of the rolls and the corresponding their successive tube-engaging surfaces being offset outwardly beyond engagement of a portion of a tube moving from one to an other of said passes.

2. A tube expanding mill, comprising a pair of skew rolls for engaging the outer surface and an interposed mandrel for engaging the inner surface of the wall of a tube, said rolls and mandrel being provided with working faces forming a plurality of successive tube-expanding passes of successively 'increasing diameters and each-of constant draft regardless of normal variations in the longitudinal position of the mandrel with relation to the rolls, said rolls between their successive tube-engaging surfaces being offset outwardly beyond engagement of a portion of a tube moving from one to another of said passes, and the central portions of the several passes being formed for uniform angular speeds to minimize slippage between a tube and the surfaces of the roll and mandrel contacting with the tube.

3. A tube expanding mill, comprising a pair of skew rolls provided with a plurality of conical working faces each contacting the outer surface of the wall of a tube in a line parallel to the axis of the tube, and a mandrel between said rolls provided with conical working faces each tapering outwardly in the direction of movement of a tube through the mill and positioned to cooperate with said conical roll faces to reduce the wall thickness and enlarge the diameter of the tube in a plurality of successive tube-engaging passes of successively increasing diameters and each of a constant draft regardless of normal variations in the longitudinal positlilon of the mandrel with relation to the ro s.

In testimony whereof, I sign my name.

RALPH G. STIEFEL. 

